Some particulate filters (PFs) may be cleaned while an engine is in operation via a process called regeneration. During regeneration, the filter is heated above its normal operating temperature to oxidize or burn off particulates that have accumulated in the filter. In addition to, or instead of, employing a heater to increase the temperature of the filter, the engine may be operated in a manner which may assist in the heating of the particulate filter.
One approach to increase the temperature of the filter during regeneration is disclosed in U.S. Pat. No. 6,959,541. In the cited reference, a fuel injection control system performs a post injection (following a main injection) late in an expansion (e.g., power) stroke or early in an exhaust stroke when heat for regeneration of a particulate filter is desired. As such, fuel is supplied to the exhaust passage which is available for oxidation by an oxidation catalyst, thus creating heat to increase the temperature of the particulate filter for regeneration.
In such a configuration, fuel is injected in a cylinder when the piston is far away from the fuel injector (e.g., the position of the piston is closer to bottom dead center than to top dead center). As a result, conditions such as cylinder wall wetting may occur which may lead to fuel-in-oil dilution and/or piston and cylinder wall degradation, for example.
The inventor herein has recognized the above problems and has devised approaches to at least partially address them. Thus, a method for controlling an engine in a vehicle, the engine having a cylinder with a bowl, is disclosed. The method comprises, during a regeneration of a particulate filter positioned in the engine exhaust, injecting fuel into one or more cylinders of the engine at least via a late post injection in an exhaust stroke of an engine cycle, the late post injection occurring sometime after approximately 40 degrees CA before top dead center such that some or all of the fuel is sprayed into the piston bowl.
Specifically, in one example, a piston configured to move within the cylinder has a face with a bowl. Because the fuel injector is close to the face of the piston after 40 degrees CA before top dead center (e.g., the position of the piston is closer to top dead center than to bottom dead center), the fuel injected via the late post injection is injected into the bowl. Further, the timing and amount of the injection may be controlled based on an amount of heat needed to increase the temperature of the particulate filter during regeneration. In this way, the temperature increase of the particulate filter may be facilitated via fuel injection while conditions which may cause degradation of the cylinder and/or other engine components, such as cylinder wall wetting, may be reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.